Chapter 5. Modifying Your Table Design
No matter how carefully you design your database, you can be sure that you’ll need to change it at some later date. Here are some of the reasons you might need to change your database.
You no longer need some of the tables.
You need to perform some new tasks that require not only creating new tables but also inserting some linking fields in existing tables.
You find that you use some fields in a table much more frequently than others, ...